Lungfish are among the most intriguing of "oddball" aquarium subjects, being able to survive in the most extreme conditions. They are very ancient fish, having remained virtually unchanged for millions of years.

The natural habitat of P. a. annectens is wet for only part of the year and the fish has developed several incredible adaptations in order to counteract this. When the waters begin to recede, the fish will find a suitable nesting site, usually amongst heavy vegetation. Here…

Lungfish are among the most intriguing of "oddball" aquarium species, being able to survive in extreme conditions. They are very ancient fish, having remained virtually unchanged for millions of years. This is the only species known from South America, and is the sole representative of its genus. Most hail from Africa, with a single species native to Australia. They belong to the class Sarcopterygii (lobe-finned fishes), members of which are actually more closely related to terrestrial…

This is one of the largest freshwater fish species in the world, and clearly shouldn’t be considered a home aquarium subject at all given its eventual size and the fact it can live for well in excess of 50 years. We include it here only because some public aquaria are able to maintain it long-term.

Unfortunately, juveniles are seen for sale quite regularly in the aquari…

Known from Great Lakes Erie and Michigan with distribution extending south through the Mississippi River basin to the Gulf of Mexico drainages where it’s said to occur between the lower Apalachicola River in Florida and the Nueces River in Texas.

It may also be found in the Rio Grande which forms the border between Mexico and the United States further south where records include Falcon International Reservoir, for example.

This species is also referred to as ‘royal knifefish’ in the aquarium trade but arguably has no place in the ornamental hobby given its adult size and specialised requirements.

It can be distinguished from congeners by presence of many small, dark spots on the anterior portion of the body which merge to form oblique, irregular stripes extending onto the anal and caudal fins posteriorly.

This species’ name has been widely misapplied in the aquarium trade and hobbyist literature, most often in reference to the Southeast Asian species C. ornata, but unlike its relative is in fact very rarely exported for ornamental purposes although its is fished and cultured for food in India.

It can be told apart from C. ornata by possessing fe…

There are currently three genera in the family Potamotrygonidae, all of which hail from South America. Paratrygon and Plesiotrygon are both monotypic genera (contain only a single described species) and are rarely seen in the hobby. The vast majority of captive rays belong to the biggest genus, Potamotrygon. This contains 17 species at present, and its members are sometimes referred to as "big-eyed" stingrays for fairly obvious reasons. There are also a number of undescribed species th…

P. falkneri is arguably among the most beautiful Potamotrygonids seen in the hobby. It's not imported with any great degree of regularity, and is usually expensive when available.

There are currently three genera in the family Potamotrygonidae, all of which hail from South America. Paratrygon and Plesiotrygon are both monotypic genera (contain only a single described species) and are rarely seen in the hobby. The vast majority of imported rays belong to the biggest genus, Potamotrygon. T…

P. hystrix is sometimes sold as P. sp. "C", and is much sought after in the hobby. The species is usually recommended as a good beginners' ray due to its relatively small adult size. However due to current Brazilian legislation regarding the export of rays it's almost never available at present, and tends to command a high price when it is. The fish sold as hystrix in the trade are almost always Peruvian in origin and erroneously labelled. We've seen P. humerosa, P. yep…

P. henlei is one of the more sought after ray species in the hobby due to its striking colours and impressive adult size. A fully grown one of these makes a stunning sight. Sadly exports from Brazil are now illegal under the IBAMA regulations, although captive bred fish are available occasionally. The price tends to be very expensive as a result.

The species exists in various colour forms, with either white or yellow spots and a background colour varying between black and dark brown. The patt…